Here we report the successful first operation of FLUMIAS-DEA, a miniaturized high-resolution 3D fluorescence microscope on the International Space Station (ISS) by imaging two scientific samples in a temperature-constant system, one sample with fixed cells and one sample with living human cells. The FLUMIAS-DEA microscope combines features of a high-resolution 3D fluorescence microscope based on structured illumination microscope (SIM) technology with hardware designs to meet the requirements of a space instrument. We successfully demonstrated that the FLUMIAS technology was able to acquire, transmit, and store high-resolution 3D fluorescence images from fixed and living cells, allowing quantitative and dynamic analysis of subcellular structures, e.g., the cytoskeleton. The capability of real-time analysis methods on ISS will dramatically extend our knowledge about the dynamics of cellular reactions and adaptations to the space environment, which is not only an option, but a requirement of evidence-based medical risk assessment, monitoring and countermeasure development for exploration class missions.

Of all 3D-super resolution techniques, structured illumination microscopy (SIM) provides the best compromise with respect to resolution, signal-to-noise ratio (S/N), speed and cell viability. Its ability to achieve double resolution in all three dimensions enables resolving 3D-volumes almost 10× smaller than with a normal light microscope. Its major drawback is noise contained in the out-of-focus-signal, which—unlike the out-of-focus signal itself—cannot be removed mathematically. The resulting “noise-pollution” grows bigger the more light is removed, thus rendering thicker biological samples unsuitable for SIM. By using a slit confocal pattern, we employ optical means to suppress out-of-focus light before its noise can spoil SIM mathematics. This not only increases tissue penetration considerably, but also provides a better S/N performance and an improved confocality. The SIM pattern we employ is no line grid, but a two-dimensional hexagonal structure, which makes pattern rotation between image acquisitions obsolete and thus simplifies image acquisition and yields more robust fit parameters for SIM.